The present invention relates to a magnetron apparatus for use in a microwave appliance, such as a microwave oven, and a method for manufacturing the magnetron apparatus.
The above-mentioned magnetron apparatus is a microwave oscillation tube operating at a fundamental frequency of, for example, 2,450 MHz and is used as a high-frequency source in an electric appliance (e.g. microwave appliance) using the microwaves. More specifically, a magnetron apparatus is used for microwave heaters such as microwave oven and industrial heater, or a gas excitation apparatus for lighting a microwave discharge lamp. This kind of magnetron apparatus generally comprises a cathode, a tubular anode disposed around the cathode and a resonant cavity formed in the inner space of the tubular anode. Furthermore, in the magnetron apparatus, as is well known, LC filter circuit components including a capacitor and choke coils are connected to the cathode to prevent leakage of high-frequency noise.
In the above-mentioned magnetron apparatus, the temperature of the cathode becomes high during operation thereof. The heat generated at the cathode heats other components, thereby adversely affecting the components. Therefore, in the magnetron apparatus, technical task must be solved to prevent adverse effects due to temperature rising during operation, thereby to prevent changes in the characteristics of the magnetron apparatus.
As a conventional magnetron apparatus developed to solve the above-mentioned problems, a liquid-cooled magnetron apparatus is disclosed in Japanese Laid-open Patent Application No. Hei 4-4544, for example.
This conventional magnetron apparatus will be described below specifically, referring to FIG. 8.
FIG. 8 is a partially cutaway sectional view showing a configuration of a conventional magnetron apparatus.
As shown in FIG. 8, the conventional magnetron apparatus comprises a magnetron part 51, a magnetic circuit part 53 for forming a magnetic circuit, and a radio wave leakage prevention part 57 for preventing leakage of high-frequency noise.
The magnetron part 51 comprises a tubular anode 52 and a cathode (not shown) disposed inside the tubular anode 52, and causes oscillation to generate a microwave having a predetermined fundamental frequency.
The magnetic circuit part 53 comprises magnets 54a and 54b disposed around the upper and lower opening end portions of the above-mentioned tubular anode 52, respectively, and a case-shaped yoke 55 containing the tubular anode 52 and the magnets 54a and 54b. The yoke 55 is provided with a supply port 56a for supplying a cooling liquid 60 to the inner space of the yoke 55 and an outlet port 56b for discharging the cooling liquid 60. The inner space of the yoke 55 is sealed with the tubular anode 52, a rubber packing members 61, and the magnets 54a and 54b. An adhesive (not shown) is coated between the yoke 55 and the magnets 54a and 54b. The inner space of the yoke 55 is filled with the cooling liquid 60, such as water, thereby directly cooling the tubular anode 52, the magnets 54a and 54b, and the yoke 55.
The radio wave leakage prevention part 57 is provided with a metallic filter case 58 and a capacitor 59, one end of which is connected to the above-mentioned cathode inside the filter case 58. The other end of the capacitor 59 is taken out of the filter case 59 as shown in FIG. 8, and connected to an electric power source (not shown).
With the above-mentioned configuration, the conventional magnetron apparatus is intended to prevent temperature rising at the tubular anode 52 and the magnets 54a and 54b during operation, thereby to decrease changes in characteristics.
However, the application voltage (electric power source voltage) of the above-mentioned conventional magnetron apparatus during operation is generally in the range of 4 to 5 kV. For this reason, in the radio wave leakage prevention part 57 of the conventional magnetron apparatus, the distance between the filter case 58 (the ground potential side) and the capacitor 59 (the electric power source potential side) disposed in the filter case 58 is required to be kept at a distance (hereinafter referred to as xe2x80x9can insulation distancexe2x80x9d) enough to withstand the above-mentioned application voltage. Therefore, the filter case 58 of the conventional magnetron apparatus cannot be made small, thereby making it difficult to miniaturize the configuration of the magnetron apparatus. Furthermore, if the insulation distance is insufficient, a discharge phenomenon occurs between the filter case 58 and the connection point to the cathode of the capacitor 59 during operation, thereby causing improper apparatus operation.
In addition, in the conventional magnetron apparatus, the heat caused at the cathode is directly transferred to the capacitor 59, thereby raising the temperature of the capacitor 59 to a high temperature of 120 to 150xc2x0 C. As a result, the capacitor 59 of the conventional magnetron apparatus is burnt and deteriorated, thereby causing a problem of lowering its noise prevention performance significantly.
The object of the present invention is to provide a magnetron apparatus that can solve the aforementioned problems in the conventional magnetron apparatus.
In order to achieve the above-mentioned object, the magnetron apparatus of the present invention comprises:
a magnetron having a tubular anode and a cathode,
a magnetic circuit having first and second magnets disposed around the upper and lower opening end portions of the tubular anode, respectively, and a yoke disposed enclosing the tubular anode and the first and second magnets, and
a radio wave leakage preventor having a filter case and LC filter circuit components disposed inside the filter case,
an insulating cooling liquid filled in at least the filter case.
According to the above-mentioned configuration, the adverse influence of temperature rising during operation is lowered, whereby burning and deterioration of the LC filter circuit components are reduced, and the magnetron apparatus can be miniaturized.
A magnetron apparatus according to another aspect of the present invention comprises: the tubular anode of the magnetron has cooling fins around the outer peripheral portion of the tubular anode, beside the aforementioned configuration.
According to the above-mentioned configuration, the temperature rising at the tubular anode and the magnets can be reduced further. In addition, this can reduce drop in the output of the magnetron apparatus.
A magnetron apparatus according to another aspect of the present invention comprises: the insulating cooling liquid is supplied from a supply port, beside the aforementioned configuration.
According to the above-mentioned configuration, the insulating cooling liquid can be supplied easily at the final manufacturing step of the magnetron apparatus, or at the time when the magnetron apparatus is installed in a microwave appliance.
A magnetron apparatus according to another aspect of the present invention comprises: the insulating cooling liquid is discharged from an outlet port, beside the aforementioned configuration.
According to the above-mentioned configuration, the insulating cooling liquid is circulated between the filter case and an outside apparatus, whereby the LC filter circuit components can be cooled efficiently. Furthermore, the temperature of the insulating cooling liquid in the magnetic circuit and the radio wave leakage preventor can be maintained at a constant value at all times. This stabilizes the noise prevention performance and the output performance of the magnetron apparatus.
A magnetron apparatus according to another aspect of the present invention comprises: a cooling liquid storage tank is provided between the supply port and the outlet port, so that the insulating cooling liquid circulates, beside the aforementioned configuration.
According to the above-mentioned configuration, the insulating cooling liquid is circulated between the filter case and an outside apparatus, whereby the LC filter circuit components can be cooled efficiently. Furthermore, the temperature of the insulating cooling liquid in the magnetic circuit and the radio wave leakage preventor can be maintained at a constant value at all times. This stabilizes the noise prevention performance and the output performance of the magnetron apparatus.
A magnetron apparatus according to another aspect of the present invention comprises: inside a space of the yoke is filled with the insulating cooling liquid, beside the aforementioned configuration.
According to the above-mentioned configuration, the tubular anode, the magnets and the yoke can be cooled directly.
A magnetron apparatus according to another aspect of the present invention comprises: the magnetic circuit is enclosed in the filter case, beside the aforementioned configuration.
According to the above-mentioned configuration, it is not necessary to change existing main components, such as the magnetron and the magnetic circuit, whereby it is possible to prevent the cost of the apparatus from rising. In other words, it is not necessary to prepare new working facilities, such as metal molds for the main components.
A magnetron apparatus according to another aspect of the present invention comprises: the yoke is a part of the filter case, beside the aforementioned configuration.
According to the above-mentioned configuration, the tubular anode, the magnets and the yoke can be cooled directly. Further, it is possible to decrease numbers of the components in the magnetron apparatus, and to miniaturize the magnetron apparatus.
A magnetron apparatus according to another aspect of the present invention comprises: a communicating portion is provided for communicating the space inside the magnetic circuit with the space inside the radio wave leakage preventor, beside the aforementioned configuration.
According to this structure, a difference in temperature occurs between the insulating cooling liquid in the magnetic circuit and the insulating cooling liquid in the radio wave leakage preventor during operation of the apparatus. This causes natural convection of the insulating cooling liquid between the magnetic circuit and the radio wave leakage preventor, thereby circulating the insulating cooling liquid.
A magnetron apparatus according to another aspect of the present invention comprises: the communicating portion is provided with the central hole of one of the magnets disposed on the side of the radio wave leakage preventor, beside the aforementioned configuration.
According to the above-mentioned configuration, the magnet on the side of the radio wave leakage preventor can be cooled efficiently. Furthermore, this prevents upsizing of the apparatus.
A method for manufacturing a magnetron apparatus comprising a magnetron, a magnetic circuit and a radio wave leakage preventor, wherein
after connecting said magnetic circuit and said radio wave leakage preventor to each other, an insulating cooling liquid is supplied into the filter case of said radio wave leakage preventor.
According to the above-mentioned configuration, the insulating cooling liquid can be supplied at the final manufacturing step of the magnetron apparatus, or at the time when the magnetron apparatus is installed in a microwave appliance. Therefore, it is possible to prevent contamination due to spill or splash of the insulating cooling liquid at steps before the final step.